This invention relates to improved chemical resistance in iron based alloys and more particularly to Fe-Cr-Ni alloy compositions containing a small amount of a metallic addition to improve chemical resistance at high temperatures.
Iron based alloys and particularly Fe-Cr-Ni alloys are construction materials for coal gasifiers, processing vessels and other equipment designed to operate at temperatures in the order of 500-1000.degree. C. In many instances, corrosive gases containing oxygen and/or sulfur are present. Under conditions of oxidation and particularly sulfidation, this equipment often has limited periods of operation before repairs or replacements are required. In addition, it is often necessary to utilize substantial amounts of chromium in these alloys to achieve reasonable performance. Chromium is an expensive component and primarily obtained from sources outside the United States.
Accordingly, one object of this invention is an improvement in the oxidative and/or sulfidative resistance of iron based alloys. A second object of the invention is a reduction in the amount of chromium required in iron based alloys under oxidative and/or sulfidative conditions. Another object of the invention is an improvement in the chemical resistance of low-chromium iron-based alloys. These and other objects will become apparent from the following detailed description.